As you shop, remember that an airplane "kit" is a box of sticks that needs to be glued together, sanded, and covered. An "ARF" is a mostly built and covered airplane that simply requires final assembly and installation of an engine and radio system. An airplane designated as RTF generally comes with an engine and radio system installed and merely requires minimal final assembly.

Building and covering your own trainer aircraft is a great way to go if you feel up to the task. You will be much more familiar with the structural and mechanical details of your airplane when you first attempt to fly it, and fixing it in the event of a mishap will be relatively simple. Building a kit is actually more costly than assembling an ARF or RTF airplane. Kits don't include items like wheels, fuel tanks, or covering that will have to be purchased seperately.

Many pilots aren't experienced at model building and prefer to focus first on the piloting aspect of our hobby (as opposed to the mechanical or building aspects). These pilots prefer to start with an ARF or RTF airplane and will later learn building and mechanical skills later after basic flight training. This approach is fine for folks without an interest in building and/or no room or time for kit assembly.

As for a specific recommendation, I'd throw in a plug for the Sig Kadet LT-25 kit. It's an easy-to-build laser cut kit with a slab-sided fuselage and a .63" wingspan. It also comes set up as a tail-dragger by default. I like tail-draggers on grass runways and tricycle gear for paved runways. Tail draggers aren't particularly difficult to fly off of pavement, but tricycle gear can be tough to fly through grass unless it's mowed frequently.

The LT-25 is as large as most .40-size trainers, but can be powered by a much less thirsty .25~.32 size 2-stroke. This plane would be a great first trainer, a great first building project, and a pleasure to fly in general.

Good luck, and good shopping!